The EU has spoken of countermeasures to the decision, including a list of US products on which to apply tariffs if Mr Trump follows through on his plan.

"We will put tariffs on Harley-Davidson, on bourbon and on blue jeans — Levi's," Mr Juncker told German television.

But it says it will conform with World Trade Organisation (WTO) rules, meaning such measures would have to apply to imports from all countries and could also hit producers including China, India, Russia, South Korea and Turkey.

Other countries are now considering tariffs as well

Canada, China, Japan and Mexico are also considering if they will retaliate.

"These tariffs are very likely to accelerate a tit-for-tat approach on trade, putting US agricultural exports in the crosshairs," executive director of Farmers for Free Trade, a group defending NAFTA at the talks, Brian Kuehl said.

China has urged the US to "show restraint" in using protective trade measures, and has options if it does consider tariffs on US imports, including suppliers of soybeans, the biggest American export to China.

A curb on purchases could hurt farm state voters who supported Mr Trump.

Canada is the largest supplier of both steel and aluminium to the US, supplying 16 per cent of US demand for steel.

Foreign Minister Chrystia Freeland said they were prepared to take responsive measures to defend its trade interests, but industry insiders say it has limited leverage to counter the plan, with officials attempting to secure an exemption from the tariffs.

Japan's Trade and Industry Minister Hiroshige Seko had this to say: "We don't think imports from Japan, an ally, have any effect at all on US national security."

South Korean trade envoy Kim Hyun-chong met with Mr Trump's chief economic adviser, Gary Cohn, and Commerce Secretary Wilbur Ross to "strongly demand" they keep the impact on local companies to a minimum, according to a Trade Ministry statement.

Brazil's Industry Ministry said it would consider taking action on its own over the tariffs or in concert with other countries, and one Mexican official said earlier this week that Mexico would hit back if subject to US tariffs.